Don't know if there is any still around but when we had that problem with a
window we did the window with Bon Ami for awhile and it solved the problem.
That is an old fashioned window cleaner that comes in a cake of white and
you wipe it on with a wet rag.Similar to white running shoe cleaner. Later
wiping it off to a cleaned window. It was still around a few years ago. Had
to do some shiny chrome hub caps once too for the sake of a robin. I would
think you could substitute something else.(the running shoe stuff)

Gerrie Patterson
Gibsons.
birdsabundant at sunshine.net